Precise orientation of continuous reinforcing fibers is critical to obtaining high performance continuous fiber reinforced glass matrix composite articles. The physical properties of such articles are anisotropic since the reinforcing fibers provide high tensile strength and high stiffness to the composite article in a direction parallel to the long axis of the reinforcing fibers. In order to obtain high tensile strength and high stiffness in more than one direction, it is necessary to orient the fiber reinforcement in more than one direction.
Two dimensionally reinforced glass matrix composite laminates may be made by hot pressing layers of glass impregnated woven fiber cloth or layers of glass impregnated unidirectionally oriented fiber tape as described in commonly assigned U.S. Pat. No. 4,581,053. Such two-dimensionally reinforced articles meet the demands of a wide variety of applications. However, in certain applications articles which exhibit high strength and stiffness in three or more noncoplanar directions are required.
Three-dimensionally reinforced glass matrix composite articles may be made by a compression molding woven fiber preforms wherein the preforms comprise glass slurry coated fibers as described in commonly assigned U.S. Pat. No. 4,581,053 or which comprise glass fibers and reinforcing fibers as described in commonly assigned U.S. Pat. No. 4,613,473. However, compression molding necessarily compacts the woven preform in one direction, and multi-dimensionally reinforced woven fiber preforms cannot be compression molded without buckling or crimping the reinforcing fibers in the direction of compaction.
A method of transfer molding fiber reinforced glass matrix composite articles, described in commonly assigned U.S. Pat. No. 4,428,763 avoids the fiber buckling and fiber crimping problems associated with compression molding processes. In the transfer molding process, the reinforcing fibers are aligned in a mold cavity and heated matrix material is injected into the mold cavity to surround the aligned fibers. The uniform infiltration of a large, tightly woven, fiber preforms with heated glass matrix material has proven to be extremely difficult due to the viscosity of the heated glass matrix material. The severity of the problems encountered increase as the volume fraction of reinforcing fibers increases.
What is needed in the art is method for making continuous fiber reinforced glass matrix composite articles which overcomes the above problems.